Dylan, in response to your questions:
1. The only way I know of to start these HT motors without pedalling them is to buy a pull-starter (look at the various sponsor websites on the left or right-hand sides of your screen, or else check Ebay). Without a pull-starter, yes - you have to pedal to start these engines.
2. Check out these websites for some inexpensive tire sourcing answers: -- Bicycles, Bike parts, Mountain Bikes, BMX, Road Bikes, Haro Bikes, KHS Bikes, Felt Bikes at Niagara Cycle Works
, Performance Bicycle - Bikes, bike accessories, bike gear, cycling equipment, cycling apparel, and more
. There are probably lots of others too - just use a search engine.
3. All-black engine kits come in a variety of packages on several of the sponsors' websites. Click on them and look around.
4. An easy (everything included) source of nitrous kits is Pirate Cycles' website (again, they're a sponsor here). As far as your "under 150cc" engine concern - be aware that most of the bicycle-adaptable engines you'll find are far under 150cc... in fact, that amount of displacement would categorize you as a motorcycle in pretty much every state, with all the accompanying legal hoopla.
Good luck with your build!!